Ocean Noise Reveals Acidification Patterns in Breakthrough Study

In what could represent a significant breakthrough for ocean monitoring, researchers have reportedly found a way to use the ocean’s natural soundscape to track dangerous acidification patterns. According to findings published in the Journal of Geophysical Research: Oceans, the method leverages ambient noise across different frequencies to measure pH changes throughout entire water columns rather than at single points.

Turning Noise into Data

The ocean’s cacophony—from whale songs and ship propellers to shrimp snapping and wave action—has long been considered background noise. Now, sources indicate this very noise could become one of our most powerful tools for understanding how carbon emissions are transforming marine chemistry.

Here’s how it apparently works: researchers discovered that two compounds in seawater, boric acid and magnesium sulfate, naturally absorb sound at specific frequencies. Crucially, rising acidity decreases boric acid’s sound-absorbing properties while leaving magnesium sulfate unaffected. By comparing how these frequencies travel through the water column, scientists can apparently calculate the integrated pH across vast ocean volumes.

Fifteen Years in the Making

The breakthrough didn’t happen overnight. Analysis suggests the research began back in 2009 with a U.S. Navy-funded cruise to the Philippine Sea. David Barclay, an acoustical oceanographer at Dalhousie University who led the work, reportedly deployed an instrument called Deep Sound at 5,000 meters depth and made an unexpected discovery.

“One immediate surprise was that the abyss wasn’t as quiet as they expected,” according to the published accounts. When surface winds exceeded 10 knots, the sounds of breaking waves reached all the way to the instrument at the seafloor.

It took five more deployments and instrument upgrades that eventually allowed operation at depths exceeding 10,000 meters in the Challenger Deep. Ernst Uzhansky, an acoustic physicist now at the Naval Postgraduate School, expressed initial skepticism about finding the signal. “I can’t tell you how happy I was,” he reportedly said. “Now it really opens up an opportunity to do large-scale pH monitoring.”

The Acidification Challenge

Ocean acidification represents one of climate change’s most insidious threats. As the ocean absorbs about one-third of annual carbon dioxide emissions, chemical reactions create bicarbonate and hydrogen ions that lower seawater pH. Ship-based measurements have already detected pH dropping from 8.11 to 8.04 since 1985—a concerning trend for marine ecosystems.

Current monitoring relies heavily on the biogeochemical Argo float network, but analysts note these provide point measurements rather than integrated water column data. The acoustic method could complement these efforts by offering broader spatial coverage, though it faces accuracy questions.

Scientific Scrutiny and Future Potential

Not everyone in the oceanographic community appears fully convinced. Liqing Jiang, a chemical oceanographer at the University of Maryland, reportedly noted the team didn’t compare its measurements with known observations, calling this “a serious flaw.”

Ken Johnson of the Monterey Bay Aquarium Research Institute, who leads the BGC-Argo program, suggested the data quality isn’t yet where it needs to be but acknowledged the potential. “With a little signal processing, who knows?” he reportedly commented.

The timing might be fortuitous. Sources indicate the future of the BGC-Argo program faces uncertainty beyond next year due to funding challenges. Honeywell previously stopped making the pH sensors used by the floats, only reversing the decision after intervention from the Biden administration.

Looking ahead, researchers plan to deploy instruments on the seafloor for extended periods to validate the method. There’s also potential for monitoring geoengineering experiments aimed at increasing coastal water alkalinity. Andone Lavery, an acoustical oceanographer at Oregon State University, suggested existing fiber optic cables on ocean floors might even detect these pH-sensitive frequencies.

If the technique proves reliable, it could transform how we monitor one of climate change’s most critical metrics—using the ocean’s own voice to tell us about its changing health.